Lore is very important in my story, even if my audience isn't seeing the machinations behind the curtain. And lore can cover anything in the overall scope of world building because everything, technically, HAS a reason for its existence even it's not immediately understood by the audience.
Even in themes like fantasy, sci-fi, supernatural/occult, some people may not realize they're thinking about it when they are. Harry Potter is a good example...people are able to bend the physics of their world for a desired outcome and we're not sure HOW they do it, but the rules of that universe dictate that it can happen. Stories can also feel more like an instruction manual in how to live there instead of the development of the people in those universes so I totally understand why people approach world building and lore like this as a sort of "meh" thing.
But then continuing with the HP example, JK Rowling gives enough information into the background of a thing to keep it relevant to the plot at that moment. The Nicholas Flammel arc, for example. We never officially meet the man, but we know it was his invention that was pivotal in the villains plan in book one.
So, for example, if you have a sacred and dangerous object your characters must find, they're going to naturally ask questions (with a few exceptions). The thief/merc archetype may not ask questions because the price may be right but then, you, as their creator, can force them to confront the lore and learn as they go ("should have done some more research, eh'?") So, yeah...lore is important as long as it has a presence/impact on the current plot of the story.
But like I said in the beginning, you could also be thinking of so much that dictates your characters thoughts and actions that pertain to lore or, rather, has roots IN lore. Religion and dogmatic points of view are a good example of how thousand+year old texts can still have impact on our present day to day.
Anyway, I could probably keep babbling. Please do forgive. xD